/*
 * Copyright 2021 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef skgpu_graphite_Uniform_DEFINED
#define skgpu_graphite_Uniform_DEFINED

#include "src/core/SkSLTypeShared.h"

namespace skgpu::graphite {
// TODO: can SkRuntimeEffect::Uniform be absorbed into this class!?

/* *
 * Describes a uniform. Uniforms consist of:
 * name:       The constant string name to use in the generated SkSL (with mangling)
 * type:       The type of the uniform
 * count:      Number of elements of 'type' in the array or kNonArray if not an array.
 */
class Uniform {
public:
    static constexpr int kNonArray = 0;

    constexpr Uniform(const char *name, SkSLType type, int count = kNonArray)
        : Uniform(name, type, count, /* isPaintColor= */ false)
    {}

    /*
     * The paint color uniform is treated special and will only be added to the uniform block
     * once. Its name will not be mangled.
     */
    static constexpr Uniform PaintColor()
    {
        return Uniform("paintColor", SkSLType::kFloat4, Uniform::kNonArray, /* isPaintColor= */ true);
    }

    constexpr Uniform(const Uniform &) = default;
    Uniform &operator = (const Uniform &) = default;

    constexpr const char *name() const
    {
        return fName;
    }
    constexpr SkSLType type() const
    {
        return static_cast<SkSLType>(fType);
    }
    constexpr int count() const
    {
        return static_cast<int>(fCount);
    }

    constexpr bool isPaintColor() const
    {
        return static_cast<bool>(fIsPaintColor);
    }

private:
    constexpr Uniform(const char *name, SkSLType type, int count, bool isPaintColor)
        : fName(name),
          fType(static_cast<unsigned>(type)),
          fIsPaintColor(static_cast<unsigned>(isPaintColor)),
          fCount(static_cast<unsigned>(count))
    {
        SkASSERT(SkSLTypeCanBeUniformValue(type));
        SkASSERT(count >= 0);
    }

    const char *fName;

    // Uniform definitions for all encountered SkRuntimeEffects are stored permanently in the
    // ShaderCodeDictionary as part of the stable ShaderSnippet and code ID assigned to the
    // effect, including de-duplicating equivalent or re-created SkRuntimeEffects with the same
    // SkSL. To help keep this memory overhead as low as possible, we pack the Uniform fields
    // as tightly as possible.
    uint32_t fType : 6;
    uint32_t fIsPaintColor : 1;
    uint32_t fCount : 25;

    static_assert(kSkSLTypeCount <= (1 << 6));
};
} // namespace skgpu::graphite

#endif // skgpu_graphite_Uniform_DEFINED
